Identification of a laminated layer-associated protein in Echinococcus multilocularis metacestodes

Abstract

Echinococcus multilocularis is a cestode parasite that predominantly infects red and arctic foxes as definitive hosts. Ingestion of E. multilocularis eggs and subsequent post-oncospheral infection with the larval stage (metacestode) of the parasite results in alveolar echinococcosis (AE), a life-threatening hepatic disease concerning humans and other intermediate hosts such as small rodents. The primary fluid-filled vesicles of the asexually proliferating metacestode are comprised of an inner germinal layer, a syncytial tegument, and an outer, acellular, so-called laminated layer. This laminated layer may play an important role in protecting the developing E. multilocularis metacestode from host immune reactions, and laminated layer-associated components represent potential targets for intervention during the course of AE. We have used an in vitro cultivation technique for the long-term maintenance and proliferation of E. multilocularis metacestodes in order to generate premature (protoscolex-free) parasite vesicles. A polyclonal antiserum was raised against this host-free parasite tissue. Subsequent immunoblot analysis of parasite fractions obtained by Triton X- 114 extraction lead to the identification of a 116 kDa protein (named EmP2) within the Triton-insoluble fraction. The characterization of EmP2 by SDS- PAGE, Western blotting, and by immunofluorescence revealed that EmP2 is a laminated layer-associated protein.